Ahead of today's opening session, the air temperature is 30 degrees C, whilst the track temperature is 37 degrees. It is approaching 6pm and there is a 20% chance of rain... which would be a first here.

First off, in terms of the circuit, since 2014 it has been re-aligned between turns 10 and 13 and now uses the left hand side of the Anderson Bridge. Also arrangements for cars to re-join the track having gone into the runoff area at turn 1 will be made, i.e. lines and bollards to follow as at the second chicane in Monza.

There are two DRS zones, the first detection point is at the exit of turn 4 and the first activation point is after turn 5. The second detection is before turn 22 and the activation point after the turn 23.

Tyres available are soft and supersoft.

There are no reserve drivers on duty today, however, at Manor Alexander Rossi makes his F1 race debut, the first of five appearances for the American youngster.

Whilst Lewis Hamilton is looking to extend his 53 point lead, teammate Nico Rosberg, who really needs to start his fight back, is using his fourth engine of the season. You'll remember that he had to change engines at Monza, swapping his upgraded unit for a six-race old version that expired three laps from the end of the race. Unwilling to take a gamble with the original upgraded unit, which has been repaired, Mercedes has instead opted to give its driver a new (upgraded) engine.

Sebastian Vettel is very confident this weekend, whilst Lotus is in action not only here but in the High court back in London where it is fighting for its financial life.

The complete opposite of Monza, here downforce is at a premium and consequently some of the cars are looking quite different to two weeks ago. Sauber has a new smaller nose, whilst Toro Rosso and Force India feature a range of updates.

Ferrari is running different floors on its two cars, Vettel running a newer version.

Williams will also be seeking an improvement here, the FW37 having struggled in the numerous slow corners at Monaco.

The lights go green and Vettel is first out of the blocks, followed by Rossi, Raikkonen, Kvyat, Stevens and Grosjean.

Whilst FP1 is usually used as a test session, not always for the race that follows, due to the fact that all remaining sessions take place later in the day, this session, in particular, is almost redundant.

Nonetheless, the flo-vis is in abundance, as are the various aero sensor devices.

Sainz is told to pit for a nose change, Toro Rosso clearly going for a back-to-back test.

Despite his cool brake, which he is told to work, Rosberg posts the first time of the day, the German crossing the line at 1:50.393. Moments later Sainz posts 54.762.

Hamilton posts 54.482 and Stevens a 2:04.333 as Vettel and Raikkonen head down the pitlane.

Rosberg (49.473) and his teammate (51.748) improve as Button complains about a problem with his radio. Moments later Raikkonen goes third with a 52.036.

Told to be careful with his clutch paddle, Rossi claims it is touching his leg. Onboard coverage shows the American really struggling with the car. Nonetheless, he posts 58.591.

As Raikkonen and Vettel go second and third, Rosberg goes quickest in S1. He maintains the pace in S2, finally crossing the line at 49.184. Elsewhere, Massa runs wide in T7.

A 51.058 sees Hulkenberg go second, as Ricciardo goes fourth ahead of Verstappen and Hamilton.

Hamilton goes wide at T2, the Briton carefully obeying the new rule and keeping to the right before rejoining.

Button is unhappy again: "The bit you've added to the cockpit on my right-hand side is not in a good place at all," he moans, "My arm keeps hitting it."

Having gone quickest in S1, Hamilton loses time behind Perez but still improves to second with a 49.677, albeit 0.493s off his teammate's pace.

Replay shows Vettel getting up close and personal with the wall at T13, indeed rubber shavings fall to the ground having been scraped from the side of his tyre.

Elsewhere, Perez makes a complete mess of T18 and is lucky to stay out of the barriers.